Adjusting a fuel on-board a vehicle

ABSTRACT

A fuel separation system includes a fuel separator configured to receive a fuel stream and separate the fuel stream, based on a volatility of the fuel stream, into a vapor stream defined by a first auto-ignition characteristic value and a first liquid stream defined by a second auto-ignition characteristic value, the second auto-ignition characteristic value greater than the first auto-ignition characteristic value; and a heat exchanger fluidly coupled between a fuel input of the fuel stream and the fuel separator, the heat exchanger configured to transfer heat from the vapor stream to the fuel stream, and output a heated fuel stream to the fuel separator and a second liquid stream defined by the first auto-ignition characteristic value.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of, and claims priority under 35U.S.C. § 120 to, U.S. patent application Ser. No. 15/044,584, entitled“Adjusting a Fuel On-Board a Vehicle,” and filed Feb. 16, 2016, theentire contents of which are incorporated by reference herein.

TECHNICAL FIELD

This disclosure relates to adjusting a fuel on-board a vehicle and, moreparticularly, dynamically separating a fuel on-board a vehicle accordingto at least one characteristic of the fuel.

BACKGROUND

Vehicles, such as cars, trucks, boats, all-terrain vehicles, andotherwise, typical use internal combustion engines for power. Theseengines require fuel, such as gasoline, diesel, or otherwise, tooperate. The fuel is often characterized by an octane or cetane number.

SUMMARY

In a general implementation, a fuel separation system includes a fuelseparator configured to receive a fuel stream and separate the fuelstream, based on a volatility of the fuel stream, into a vapor streamdefined by a first auto-ignition characteristic value and a first liquidstream defined by a second auto-ignition characteristic value, thesecond auto-ignition characteristic value greater than the firstauto-ignition characteristic value; and a heat exchanger fluidly coupledbetween a fuel input of the fuel stream and the fuel separator, the heatexchanger configured to transfer heat from the vapor stream to the fuelstream, and output a heated fuel stream to the fuel separator and asecond liquid stream defined by the first auto-ignition characteristicvalue.

In an aspect combinable with the general implementation, the heatexchanger is configured to condense the vapor stream to the secondliquid stream defined by the first auto-ignition characteristic value.

Another aspect combinable with any of the previous aspects furtherincludes a heater coupled between the heat exchanger and the fuelseparator and configured to receive the heated fuel stream and furtherheat the heated fuel stream.

Another aspect combinable with any of the previous aspects furtherincludes a variable orifice fluidly coupled between the heat exchangerand the fuel separator.

Another aspect combinable with any of the previous aspects furtherincludes a controller operatively coupled to control at least one of thefuel separator or the variable orifice to vary a volumetric flow rate ofat least one of the heated fuel stream, the vapor stream, or the firstliquid stream.

In another aspect combinable with any of the previous aspects, thecontroller is configured to vary at least one of the first auto-ignitioncharacteristic value or the second auto-ignition characteristic valuebased, at least in part, on at least one engine operating condition.

In another aspect combinable with any of the previous aspects, the atleast one engine operating condition includes an engine load, an enginetorque, and engine speed, a fuel vapor-liquid ratio, a fuel vapor lockindex, a fuel drivability index, a fuel T90 or T95 property, a fuellubricity, a fuel viscosity, or an engine speed-torque ratio.

In another aspect combinable with any of the previous aspects, the fuelseparator includes a flash distillation separator.

In another aspect combinable with any of the previous aspects, the fuelseparator includes a first stage fuel separator and a second stage fuelseparator.

In another aspect combinable with any of the previous aspects, the firststage fuel separator is configured to receive the fuel stream andseparate the fuel stream, based on the volatility of the fuel stream,into the vapor stream defined by the first auto-ignition characteristicvalue and the first liquid stream defined by the second auto-ignitioncharacteristic value.

In another aspect combinable with any of the previous aspects, thesecond stage fuel separator is configured to separate the vapor streaminto an oxygenate stream and a compound stream.

In another aspect combinable with any of the previous aspects, thesecond stage fuel separator is configured to direct the oxygenate streamto combine with the first liquid stream, and to direct the compoundstream to the heat exchanger.

In another aspect combinable with any of the previous aspects, the firstauto-ignition characteristic value includes a first research octanenumber (RON) or a first cetane number, and the second auto-ignitioncharacteristic value includes a second RON or a second cetane number.

In another general implementation, a method for separating a fuelon-board a vehicle includes separating, with a fuel separator, a heatedfuel stream into a vapor stream and a first liquid stream based on avolatility of the fuel stream, the vapor stream defined by a firstauto-ignition characteristic value and the first liquid stream definedby a second auto-ignition characteristic value, the second auto-ignitioncharacteristic value greater than the first auto-ignition characteristicvalue; supplying an unheated fuel stream and the vapor stream from thefuel separator to a heat exchanger; transferring heat from the vaporstream to the unheated fuel stream to heat the unheated fuel stream;supplying the heated fuel stream to the fuel separator; and supplying asecond liquid stream defined by the first auto-ignition characteristicvalue from the heat exchanger.

An aspect combinable with the general implementation further includescondensing, with the heat exchanger, the vapor stream to form the secondliquid stream.

Another aspect combinable with any of the previous aspects furtherincludes further heating the heated fuel stream; and supplying thefurther heated fuel stream to the fuel separator.

In another aspect combinable with any of the previous aspects, furtherheating the heated fuel stream includes at least one of: heating theheated fuel stream with an electric heater; heating the heated fuelstream in a heat exchanger with the first liquid stream; or heating theheated fuel stream in a heat exchanger with an engine exhaust gasstream.

Another aspect combinable with any of the previous aspects furtherincludes circulating the heated fuel stream through a variable orificefluidly coupled between the heat exchanger and the fuel separator.

Another aspect combinable with any of the previous aspects furtherincludes controlling at least one of the fuel separator or the variableorifice to vary a volumetric flow rate of at least one of the heatedfuel stream, the vapor stream, or the first liquid stream.

Another aspect combinable with any of the previous aspects furtherincludes varying at least one of the first auto-ignition characteristicvalue or the second auto-ignition characteristic value based, at leastin part, on at least one engine operating condition.

In another aspect combinable with any of the previous aspects, the atleast one engine operating condition includes an engine load, an enginetorque, an engine speed, a fuel vapor-liquid ratio, a fuel vapor lockindex, a fuel drivability index, a fuel T90 or T95 property, a fuellubricity, a fuel viscosity, or an engine speed-torque ratio.

In another aspect combinable with any of the previous aspects, the fuelseparator includes a flash distillation separator.

In another aspect combinable with any of the previous aspects, the fuelseparator includes a first stage fuel separator and a second stage fuelseparator.

Another aspect combinable with any of the previous aspects furtherincludes separating, with the first stage fuel separator, the heatedfuel stream into the vapor stream defined by the first auto-ignitioncharacteristic value and the first liquid stream defined by the secondauto-ignition characteristic value, based on the volatility of the fuelstream, and separating, with the second stage fuel separator, the vaporstream into an oxygenate stream and a compound stream.

Another aspect combinable with any of the previous aspects furtherincludes combining the oxygenate stream with the first liquid stream;and supplying the compound stream to the heat exchanger.

In another aspect combinable with any of the previous aspects, hereinthe first auto-ignition characteristic value includes a first researchoctane number (RON) or a first cetane number, and the secondauto-ignition characteristic value includes a second RON or a secondcetane number.

In another general implementation, a vehicle system includes a vehicle;a fuel-powered internal combustion engine mounted in the vehicle; anon-board fuel separation system that includes a fuel separatorconfigured to receive a fuel stored in the vehicle and separate thefuel, based on a volatility of the fuel stream, into a vapor streamdefined by a first auto-ignition characteristic value and a first liquidstream defined by a second auto-ignition characteristic value, thesecond auto-ignition characteristic value greater than the firstauto-ignition characteristic value; and a heat exchanger fluidly coupledbetween a fuel input of the fuel and the fuel separator, the heatexchanger configured to transfer heat from the vapor stream to the fuel,and output a heated fuel stream to the fuel separator and a secondliquid stream defined by the first auto-ignition characteristic value; afirst fuel tank fluidly coupled between the engine and the fuelseparator to store the first liquid stream output from the fuelseparator; and a second fuel tank fluidly coupled between the engine andthe heat exchanger to store the second liquid stream output from theheat exchanger.

In an aspect combinable with the general implementation, the heatexchanger is configured to condense the vapor stream to the secondliquid stream defined by the first auto-ignition characteristic value.

Another aspect combinable with any of the previous aspects furtherincludes a controller operatively coupled to control at least one of thefuel separator or the variable orifice to vary a volumetric flow rate ofat least one of the heated fuel stream, the vapor stream, or the firstliquid stream.

In another aspect combinable with any of the previous aspects, thecontroller is configured to vary at least one of the first auto-ignitioncharacteristic value or the second auto-ignition characteristic valuebased, at least in part, on at least one engine operating condition ofthe engine.

In another aspect combinable with any of the previous aspects, the atleast one engine operating condition includes an engine load, an enginetorque, an engine speed, a fuel vapor-liquid ratio, a fuel vapor lockindex, a fuel drivability index, a fuel T90 or T95 property, a fuellubricity, a fuel viscosity, or an engine speed-torque ratio.

Another aspect combinable with any of the previous aspects furtherincludes a turbine that includes an input fluidly coupled to the fuelseparator and output fluidly coupled to the heat exchanger andconfigured to receive the vapor stream from the fuel separator andgenerate electrical power based on a pressure difference of the vaporstream between the input and the output.

In another aspect combinable with any of the previous aspects, the firstauto-ignition characteristic value includes a first research octanenumber (RON) or a first cetane number, and the second auto-ignitioncharacteristic value includes a second RON or a second cetane number.

Other aspects include: electrical power generated by a turbine can bestored and then utilized to heat the separation system at engine startup, or used in running auxiliary units or hybrid systems; two tanks tostore two separated streams could be eliminated by dynamic control (oftemperature for example) to get the appropriate volumetric flow rate andoctane number of each of the two separated streams; minimization of heatexchanger size (or reboiler in case of distillation unit) can beaccomplished by keeping a liquid under a particular pressure (about 10bar) to prevent phase change within the heat exchanger; vaporization maytake place once a liquid passes a control valve (for example, anorifice) and enters the flash or distillation unit at the operatingpressure; for better condensation of the vapor phase, the flash tank ordistillation column could be operated at a pressure above theatmospheric pressure, which may lead to full condensation with lesscooling (at higher temperatures), provided that the vapor stream remainsunder pressure until condensed or injected in the engine; and solarpanels could be fitted to the vehicle and the electrical power generatedused to run the components that needs electricity, such as pumps, anyvalves or control systems, and otherwise.

Implementations according to the present disclosure may include one ormore of the following features. For example, implementations can reducefuel consumption, fuel cost, as well as CO₂ emissions from vehicles. Asanother example, fuel consumption of a vehicle may be reduced bysupplying the engine of the vehicle with a fuel that has an optimizedauto-ignition characteristic value (for example, octane, cetane, orotherwise), rather than a higher volumetric flow rate of fuel. Forinstance, implementations may supply the engine with a fuel of aparticular optimized auto-ignition characteristic value based on engineload or operating conditions. Such implementations may optimize theauto-ignition characteristic value of a single source of fuel stored onthe vehicle (for example, in a fuel tank). Implementations describedherein may also provide an additional energy source to power componentsof the vehicle by optimizing the auto-ignition characteristic value offuel. Additionally, implementations described herein may optimize theauto-ignition characteristic value of fuel on-board the vehicle. Asanother example, implementations disclosed herein may provide formultiple fuel streams, each with different auto-ignition characteristicvalues, from a single fuel source stored on an operating vehicle. As yetanother example, implementations may allow a vehicle driver to purchasea fuel with a low auto-ignition characteristic value (for example, lowoctane number), which is typically more cost-efficient, while stillallowing the vehicle to use both the purchased fuel and a separated,higher value, fuel. As a further example, implementation may provide anadditional source of electrical power (for example, in addition toconventional sources of electrical power on a vehicle) to powercomponents of the vehicle.

The details of one or more implementations of the subject matterdescribed in this disclosure are set forth in the accompanying drawingsand the description below. Other features, aspects, and advantages ofthe subject matter will become apparent from the description, thedrawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a multi-fuel vehicle system thatincludes an example implementation of an on-board fuel separation systemaccording to the present disclosure.

FIG. 2 is a schematic illustration of an example implementation of anon-board fuel separation system according to the present disclosure.

FIG. 3 is a schematic illustration of another example implementation ofan on-board fuel separation system according to the present disclosure.

FIG. 4 is a schematic illustration of another example implementation ofan on-board fuel separation system according to the present disclosure.

FIGS. 5A-5C are graphs that illustrate results of a simulation model ofan on-board fuel separation system according to the present disclosure.

FIGS. 6A-6C are graphs that illustrate results of another simulationmodel of an on-board fuel separation system according to the presentdisclosure.

FIGS. 7A-7B are graphs that illustrate results of another simulationmodel of an on-board fuel separation system according to the presentdisclosure

FIG. 8 is a schematic illustration of an example controller for anon-board fuel separation system according to the present disclosure.

DETAILED DESCRIPTION

The present disclosure describes a fuel separation system that may bemounted on-board a vehicle, such as a car, truck, boat, or other vehiclethat utilizes an engine to generate motive power. In some aspects, thefuel separation system includes a fuel separator, such as a flashdistillation unit, that is controllable to separate an input fuel streaminto two or more fractional fuel streams based on a volatilitydifference of fractional components of the fuel. The separatedfractional fuel components are each defined by a particularauto-ignition characteristic value, such as, for example, researchoctane number (RON), cetane number, or otherwise. The auto-ignitioncharacteristic values of the separated fractional fuel components mayvary, thus resulting in a fractional fuel component stream that has alower value than another fractional fuel component stream from the fuelseparator. In some aspects, an operating condition of the fuelseparator, or one or more additional components of the on-board fuelseparation system, is controlled based at least in part on an operatingcondition of the engine. In some aspects, the on-board fuel separationsystem includes a heat exchanger that is positioned to facilitate atransfer of heat from one or more fractional fuel component streams to asource fuel stream (for example, from a fuel tank of the vehicle).

FIG. 1 is a schematic illustration of a vehicle system 100 that includesan example implementation of an on-board fuel separation system 108according to the present disclosure. As illustrated in FIG. 1, thevehicle system 100 includes a vehicle 100, which is represented as anautomobile, but the present disclosure contemplates that a “vehicle” caninclude an automobile, motorized cycle, all-terrain vehicle (ATV),nautical vehicle (for example, boat or otherwise), or an airbornevehicle (for example, plane, ultralight, drone, or otherwise), whethermanned or unmanned. Indeed, the present disclosure contemplates that a“vehicle” is any apparatus that derives powered movement from ahydrocarbon liquid fuel, such as gasoline, naphtha, or diesel asexamples. A “vehicle” may also be any apparatus that includes an enginedesigned to use a fuel having an auto-ignition characteristic value,such as research octane number (RON) (or octane rating) (for example, inthe case of gasoline fuels) or cetane number (for example, in the caseof diesel fuels).

The illustrated vehicle 102 includes a fuel input 104 that is fluidlycoupled to the on-board fuel separation system 108 to provide a fuelstream 106 to the separation system 108, for example, during operationof the vehicle 102. In some aspects, a fuel tank (not shown) is fluidlycoupled in between the fuel input 104 and the on-board fuel separationsystem 108, for example, to contain a particular volume of fuel stream106. In such aspects, the fuel stream 106 may be variably circulated(for example, pumped) from the fuel tank to the on-board fuel separationsystem 108, for example, as necessary for operation of the vehicle 102.In some aspects, a fuel rail of the vehicle could also be used forcirculation of the fuel stream 106.

As described herein, the on-board fuel separation system 108 separatesthe fuel stream 106 into two or more individual fraction streams basedon, for example, a particular characteristic of the fuel stream 106. Forexample, the fuel stream 106 may be separated into fractions based on avolatility difference of the fractions within the fuel stream 106. Thefuel stream 106, in some aspects, may be separated into an aromatic oroxygenate fraction as well as other compound fractions. In some aspects,the on-board fuel separation system 108 may include one or more fuelseparators, such as flash distillation separators (for example, flashtanks or compact distillation units or otherwise), that separate thefuel stream 106 based on the volatility difference of the fractions intoseparate fractions, each having distinct auto-ignition characteristicvalues (for example, RON, cetane number, or otherwise).

In some aspects, the on-board fuel separation system 108 may becontrollably operated at multiple pressures, multiple temperature, orboth, to optimize the auto-ignition characteristic value of theseparated fractions (for example, RON, cetane number, or otherwise), aparticular flow rate of the separated fractions, or both. Furthercontrollable aspects of the on-board fuel separation system 108 include,for example, a temperature profile of a compact distillation unit withinthe on-board fuel separation system 108, a number of equilibrium stageswithin the on-board fuel separation system 108, feed location, andreflux ratio.

The illustrated vehicle 102 includes two or more fuel fraction conduitsshown as 110 and 112, which fluidly couple the on-board fuel separationsystem 108 to fractional fuel tanks 114 and 116. For example, the fuelfraction conduit 110 may fluidly couple the on-board fuel separationsystem 108 to the fractional fuel tank 114 to store a fuel fractionoutput by the on-board fuel separation system 108 that has a particularauto-ignition characteristic value, while the fuel fraction conduit 112may fluidly couple the on-board fuel separation system 108 to thefractional fuel tank 116 to store another fuel fraction output by theon-board fuel separation system 108 that has a different auto-ignitioncharacteristic value. In particular implementations, the fractional fueltank 114 may store a fuel fraction output by the on-board fuelseparation system 108 that has a higher RON relative to a fuel fractionoutput by the on-board fuel separation system 108 that is stored in thefractional fuel tank 116. Although only two fractional fuel tanks areshown, the present disclosure contemplates that more than two fractionalfuel tanks may be fluidly coupled to the on-board fuel separation system108 (for example, depending on the number of separation stages of theon-board fuel separation system 108).

In some aspects, the two fuel streams 118 and 120 may each be feddirectly to the engine 124. For example, one fuel stream (of fuelstreams 118 and 120) could by port-injected and the other fuel stream(of fuel streams 118 and 120) could be directly injected into thecylinders of the engine 124. This implementation may avoid any time lagin providing the correct fuel to the engine 124, as a time lag couldresult from the fuel already in the fuel line after valve 122. In someaspects, the fuel route for the fuel streams 118 and 120 is kept asshort as possible.

In this example schematic illustration, the fractional fuel tanks 114and 116 are fluidly coupled to an engine 124 (for example, internalcombustion gasoline, naphtha, or diesel engine) through fractional fuelsupply lines 118 and 120 and a control valve 122. For example, thefractional fuel tank 114 (for example, which stores a higher RON fuelfraction) is fluidly coupled to the engine 124 through the supply line118, while the fractional fuel tank 116 (for example, which stores alower RON fuel fraction) is fluidly coupled to the engine 124 throughthe supply line 120. Based on, for example, dynamic (for example,instantaneous or real-time) driving conditions, such as speed vs. torqueconditions, the control valve 122 may be controlled (for example, by avehicle control system, not shown) to supply a particular fuel fractionstored in one of the fractional fuel tanks 114/116 to the engine 124.The supplied fuel fraction may have an auto-ignition characteristicvalue (for example, RON or cetane number) optimized for the dynamic (forexample, instantaneous or real-time) driving conditions. For example, ahigher RON fuel fraction (for example, stored in tank 114) may becirculated to the engine 124 based on high load engine conditions, highspeed engine conditions, or a combination thereof. A lower RON fuelfraction (for example, stored in tank 116) may be circulated to theengine 124 based on low load engine conditions, low speed engineconditions, or a combination thereof.

In some aspects, the on-board fuel separation system 108 may help reducefuel consumption, cost and CO₂ emissions. For example, depending onengine operating requirements (for example, dynamic or in real-time), afuel fraction that has minimum required auto-ignition characteristicvalue (for example, RON) is supplied to the engine 124 (and not more asis conventional). Therefore, the on-board fuel separation system 108 maystore a relatively high RON fuel fraction (for example, in fractionalfuel tank 114) for the high load and high speed operating conditions.Similarly, a relatively low RON fuel fraction is stored (for example, infractional fuel tank 116) for low load and low speed operatingconditions.

In some aspects, the fractional fuel tanks 114 and 116 may be eliminatedfrom the system 100, and, thus, one of the fuel fractions (for example,a higher RON fraction or lower RON fraction) may be circulated inreal-time (for example, during operation of the engine 124 to power thevehicle 102) from the on-board fuel separation system 108 to the engine124 as dictated by the engine operating conditions (for example, speedvs. torque, engine map operating point, or otherwise). Thus, in someaspects, the only fuel storage tank on the vehicle 102 may be fluidlycoupled between the fuel input 104 and the on-board fuel separationsystem 108 (for example, a standard vehicle fuel tank). Therefore, insome aspects, the on-board fuel separation system 108 may be integratedinto a conventional vehicle 102 that includes a single fuel tank.

FIG. 2 is a schematic illustration of an example implementation of anon-board fuel separation system 200 according to the present disclosure.In some aspects, at least a portion of the system 200 may be implementedas the on-board fuel separation system 108 in the vehicle 102 shown inFIG. 1. The illustrated on-board fuel separation system 200 includes anon-board fuel separation sub-assembly 202 (designated by the dashedline) that includes several components. As illustrated, the fuel stream106 may be received at a heat exchanger 204 (for example, a plate andframe heat exchanger, shell and tube heat exchanger, fin and tube heatexchanger, or otherwise). The heat exchanger 204 also receives an inputof a vapor fuel stream 216 that is output from the on-board fuelseparation sub-assembly 202 and circulated back to the heat exchanger204.

The heat exchanger 204 outputs a heated fuel stream 206 to a secondaryheater 208 (for example, hot coolant, hot exhaust gas, electric heateror otherwise). An orifice 210 (for example, valve, fixed orifice,variable orifice, or otherwise) is fluidly coupled between the heater208 and a fuel separator 214. A fuel stream input 212 from the orifice210 provides the heated fuel stream 206 (for example, at increased ordecreased pressure) to the fuel separator 214.

In some aspects, the fuel separator 214 may be operated at a vacuum. Forexample, in some implementations in which a particular auto-ignitioncharacteristic value is desired, the fuel separator 214 may be operatedunder a vacuum (for example, lower than ambient operating pressure) torecover increased high volatility components of the fuel stream input212.

The fuel separator 214, in the illustrated implementation of system 200,separates the fuel stream input 212 into two fuel fraction streams: thevapor fuel stream 216 and a liquid fuel stream 217. In this example, theliquid fuel stream 217 may be supplied to the fractional fuel tank 114.

The illustrated fuel separator 214 may be a flash distillation assemblythat separates the input fuel stream 212 into at least two separate fuelfractions (for example, vapor stream 216 and liquid stream 217) based ona relative volatility of the fractional components of the input fuelstream. In some aspects, the flash distillation assembly may include oneor more flash tanks that are fitted with screens or similar internalstructures to prevent or reduce liquid droplets (mist) from beingcarried with the vapor stream 216. In some aspects, the flashdistillation assembly may be a compact distillation unit filled withstructured or random packing, or with trays, to improve the separationand prevent or reduce mist carryover into the vapor stream 216. Further,in some aspects, a number of flash tanks in the flash distillationassembly may be determined by, for example, components of the fuelstream 106 (for example, linear alkanes, branched alkanes, cyclicalkanes, alkenes, aromatics) and their relative volatility, thevolatility of additives of the fuel stream 106 such as oxygenates,desired auto-ignition characteristic value of the vapor stream 216 andthe liquid stream 217, relative flow rates of the vapor stream 216 andthe liquid stream 217, or a combination thereof. Although two outputstreams (for example, the vapor stream 216 and the liquid stream 217)are shown from the fuel separator 214, more than two output streams (forexample, based on a number of fuel separation stages, flash tanks, orotherwise).

The illustrated system 200 also includes a control system 218 that iscommunicably coupled to the on-board fuel separation sub-assembly 202(for example, communicably coupled to control one or more of thecomponents, as well as unillustrated components, of the on-board fuelseparation sub-assembly 202). In some aspects, the control system 218may be a mechanical, pneumatic, electro-mechanical, or micro-processorbased control system (or a combination thereof). The control system 218may receive (or store) inputs associated with engine operatingcharacteristics of an engine of a vehicle that includes the on-boardfuel separation system 200 and, based on the received (or stored)inputs, send control signals to, for example, one or more valves thatadjust or control the temperature, the flow rates of the fuel stream106, the heated fuel stream 206, the vapor stream 216, the liquid stream217, or a combination thereof. The control system 218 may also becommunicably coupled to the fuel separator 214 to control, for example,operating temperature, pressure, or pressures, of the flash tank(s) inthe fuel separator 214. The control system 218 may also be communicablycoupled to the secondary heater 208 to, for example, further add heat tothe heated fuel stream 206 prior to the fuel separator 214.

Example engine operating characteristics include, for example, engineload, torque and speed and fuel specifications such as vapor-liquidratio, a vapor lock index, a drivability index, a T90 or T95 property, afuel lubricity, a fuel viscosity, or an engine speed-torque ratio, amongother examples. Such characteristics (as inputs to the control system218) may be used, at least in part, to adjust one or more operatingcharacteristics of the on-board fuel separation system 202. For example,operating pressure, temperature, or both of the heat exchanger 204, thefuel separator 214, or both, may be adjusted. Flow rates, pressures,temperature, or a combination thereof, of one or more of the illustratedfuel streams (for example, the fuel stream 106, the heated fuelstream(s), the vapor fuel stream 216, the liquid fuel stream 217, orotherwise) may also be adjusted (for example, by controlling valves, notshown, with the control system 218). By adjusting one or more componentsof the on-board fuel separation system 202 with the control system 218,the auto-ignition characteristic values of one or both of the vapor fuelstream 216 and the liquid fuel stream 217 may be adjusted, for example,to desired values according to engine operating conditions.

In some implementations, at high load, gasoline engines require highoctane (for example, long ignition delay) fuel to avoid knocking andengine damage. The octane of the liquid stream 217 may be high octane,and the flow rate may be determined by a temperature of the fuelseparator 214 (for example, at constant pressure) as shown graphicallyin FIGS. 5A-5C, 6A-6C. In some aspects, the on-board controller 218 mayhave an estimate of the amount of the high RON fuel (and associated RONvalue) based on a factory setting, driving history, or both. Thecontroller 218 may have predictive functions that give the RON and flowvalues at each temperature of the fuel separator 214, and the fuelspecifications (for example, vapor lock index, T95, and otherspecifications). The controller 218 may then set the fuel separator 214temperature to an optimum value to maximize the amount of the high RONfuel (liquid stream 217) by allowing more or less heat in the heater208, as needed. For other applications, the temperature could be chosento maximize the RON value at a fixed high RON stream. Another functionof the controller 218 may be to keep a minimum level of liquid in thefuel separator 214 to avoid some vapor going to the liquid tank 114.This could be accomplished by having a control valve in the conduit forthe liquid stream 217.

For compact distillation implementation, the octane numbers and the flowrates of the vapor stream 216 and liquid stream 217 may be determined bymore than one variable: the temperatures of a reboiler and a condenser(for example, for the vapor stream 216) and a number of equilibriumstages, reflux ratio and an amount of condensate drawn from thecondenser (at a fixed pressure). This control strategy may be similar tothat described above, but with more variables to control, and there isno liquid holdup in the fuel separator 214.

In some aspects, the separation system 200 may be unlikely to follow thefast dynamics of the engine in real-time. Thus, in some implementation,a vehicle with the on-board fuel separation system 200 may include twosmaller tanks, 114 and 116, (in addition to a main fuel tank) for thetwo separated fuel streams 216 and 217.

The illustrated vapor stream 216 and liquid stream 217 may havedifferent auto-ignition characteristic values. For example, in someaspects, the vapor stream 216 may have an auto-ignition characteristicvalue that is less than an auto-ignition characteristic value of theliquid stream 217. In some aspects, the auto-ignition characteristicvalues of the vapor stream 216 and the liquid stream 217 may be RON orcetane number.

In an example operation, the fuel stream 106 is circulated (for example,forcibly pumped, sprayed, or otherwise) to the heat exchanger 204, aswell as the vapor stream 216 output from the fuel separator 214. Heatfrom the vapor stream 216 is transferred, in the heat exchanger 204, tothe fuel stream 106 and output from the heat exchanger 204 as the heatedfuel stream 206. The vapor stream 216, which has a particularauto-ignition characteristic value (for example, a low RON relative tothe RON of the liquid stream 217), condenses in the heat exchanger 204as heat is transferred to the fuel stream 106. The condensed vaporstream 219 (now as a liquid stream with the low RON) may be circulatedto the fractional fuel tank 116 and stored for use as a fuel source foran engine (for example, engine 124).

In some aspects, prior to circulation of the fuel stream 106 to the heatexchanger 204, the fuel stream 106 may be preheated, for example, withelectric heating, heating tape, or otherwise. For example, in “coldstart” situations (for example, where the engine of the vehicle is beingstarted), the fuel stream 106 may be preheated based on an inability ofthe vapor stream 216, or the heating stream through heater 208, toprovide sufficient heat, in the cold start situation, to the fuel stream106. In such aspects, one or more of the fuel fractions (for example,the low RON, condensed vapor phase 219 or the high RON liquid phase 217)stored in the fractional fuel tanks 116 and 114 may be used as the coldstart fuel for the engine.

In some aspects, the vapor stream 216 may not completely condense to aliquid in the heat exchanger 204. In such aspects, the partiallycondensed vapor stream 219 may be further cooled to more completelycondense any remaining vapor in the stream 219. For example, the vaporin the partially condensed vapor stream 219 may be separated andcirculated to the engine with an air intake to the engine. As anotherexample, a secondary heat exchanger (not shown) such as a cooling coil,radiator, or otherwise, may further cool the vapor stream 219 (forexample, with a cold refrigerant that is part of the vehicleair-conditioning system) between the heat exchanger 204 and thefractional fuel tank 116. As yet another example, a pressure of thepartially condensed vapor stream 219 may be increased to further orfully condense the stream 219 prior to the fractional fuel tank 116.

The heated fuel stream 206 is circulated through the secondary heater208, which may add additional heat to the heated fuel stream 206. Forexample, the secondary heater 208 may be controlled (for example, by thecontrol system 218) to add additional heat so that particularauto-ignition characteristic values (for example, RON or cetane number)may be met in the vapor stream 216 and the liquid stream 217.

The heated fuel stream 206 (further heated by the secondary heater 208or otherwise) is circulated through the orifice 210 and into the fuelseparator 214 as the fuel stream input 212. In some aspects, the orifice210 may be controlled (for example, by the control system 218) to adjusta pressure of the fuel input stream 212 so that particular auto-ignitioncharacteristic values (for example, RON or cetane number) may be met inthe vapor stream 216 and the liquid stream 217.

The fuel input stream 212 is circulated through the fuel separator 214and separated (for example, based on relative volatilities of thefractions of the fuel input stream 212) into the illustrated vaporstream 216 and the illustrated liquid stream 217. In some aspects, thefuel separator 214 may separate the fuel input stream 212 into multiplevapor streams and multiple liquid streams, each with a particularauto-ignition characteristic value (for example, RON or cetane number).In such aspects, the fuel separator 214 (for example, flash tanks ordistillation units or combination thereof) may have multiple separationstages.

The liquid stream 217 output from the fuel separator 214, in thisexample, has an auto-ignition characteristic value (for example, RON)that is higher than the auto-ignition characteristic value of the vaporstream 216. The liquid stream 217 is circulated to the fractional fueltank 114 and stored for use as a fuel source for an engine (for example,engine 124).

FIG. 3 is a schematic illustration of another example implementation ofan on-board fuel separation system 300 according to the presentdisclosure. In some aspects, at least a portion of the system 300 may beimplemented as the on-board fuel separation system 108 in the vehicle102 shown in FIG. 1. System 300 may be similar to system 200, shown inFIG. 2, but also includes a power generator 318 that is fluidly coupledbetween a fuel separator 314 and a heat exchanger 304 within theon-board fuel separation sub-assembly 302. The power generator 318 maygenerate power (for example, electrical power), P, within a vehicle (forexample, vehicle 102) that includes the on-board fuel separation system300.

The illustrated on-board fuel separation system 300 includes an on-boardfuel separation sub-assembly 302 (designated by the dashed line) thatincludes several components. As illustrated, the fuel stream 106 may bereceived at a heat exchanger 304 (for example, a plate and frame heatexchanger, shell and tube heat exchanger, fin and tube heat exchanger,or otherwise). The heat exchanger 304 also receives an input of a vaporfuel stream 316 that is output from the on-board fuel separationsub-assembly 302 and circulated back to the heat exchanger 304.

The heat exchanger 304 outputs a heated fuel stream 306 to a secondaryheater 308 (for example, hot coolant, hot exhaust gas, electric heateror otherwise). An orifice 310 (for example, valve, fixed orifice,variable orifice, or otherwise) is fluidly coupled between the heater308 and a fuel separator 314. A fuel stream input 312 from the orifice310 provides the heated fuel stream 306 (for example, at increased ordecreased pressure) to the fuel separator 314.

The fuel separator 314, in the illustrated implementation of system 300,separates the fuel stream input 312 into two fuel fraction streams: thevapor fuel stream 316 and a liquid fuel stream 317. In this example, theliquid fuel stream 317 may be supplied to the fractional fuel tank 114.

In some aspects, the fuel separator 314 may be operated at a vacuum. Forexample, in some implementations in which a particular auto-ignitioncharacteristic value is desired, the fuel separator 314 may be operatedunder a vacuum (for example, lower than ambient operating pressure) torecover increased high volatility components of the fuel stream input312. In still further aspects, for example in implementations thatinclude the power generator 318, the fuel separator 314 may be operatedat higher pressures (for example, pressures above ambient pressure) byregulating a pressure, a temperature, or both, of the separator 314 (forexample, with a back pressure regulator downstream of the separator314). In such aspects, the pressurized vapor stream 316 may drive thepower generator 318. Power from the power generator 318 may be used, forexample, as turbocharging, supercharging, electricity, or a combinationthereof.

The illustrated fuel separator 314 may be a flash distillation assemblythat separates the input fuel stream 312 into at least two separate fuelfractions (for example, vapor stream 316 and liquid stream 317) based ona relative volatility of the fractional components of the input fuelstream. In some aspects, the flash distillation assembly may include oneor more flash tanks that are fitted with screens or similar internalstructures to prevent or reduce liquid droplets (mist) from beingcarried with the vapor stream 316. In some aspects, the flashdistillation assembly may be a compact distillation unit filled withstructured or random packing, or with trays, to improve the separationand prevent or reduce mist carryover into the vapor stream 316. Further,in some aspects, a number of flash tanks in the flash distillationassembly may be determined by, for example, components of the fuelstream 106 (for example, linear alkanes, branched alkanes, cyclicalkanes, alkenes, aromatics) and their relative volatility, thevolatility of additives of the fuel stream 106 such as oxygenates,desired auto-ignition characteristic value of the vapor stream 316 andthe liquid stream 317, relative flow rates of the vapor stream 316 andthe liquid stream 317, or a combination thereof. Although two outputstreams (for example, the vapor stream 316 and the liquid stream 317)are shown from the fuel separator 314, more than two output streams (forexample, based on a number of fuel separation stages, flash tanks, orotherwise).

The power generator 318 is fluidly coupled within the vapor stream 316between the fuel separator 314 and the heat exchanger 304. The powergenerator 318, in some aspects, may be a turbine or micro-turbinemounted in the vehicle that receives the vapor stream 316 at aparticular pressure, which turns the turbine to generate power, P, andoutputs the vapor stream 316 at a reduced pressure to the heat exchanger304. The auto-ignition characteristic value (for example, RON or cetanenumber) of the vapor stream 316 may remain unchanged or substantiallyunchanged as the vapor stream 316 rotates the power generator and losespressure.

The illustrated system 300 also includes a control system 322 that iscommunicably coupled to the on-board fuel separation sub-assembly 302(for example, communicably coupled to control one or more of thecomponents, as well as unillustrated components, of the on-board fuelseparation sub-assembly 302). In some aspects, the control system 322may be a mechanical, pneumatic, electro-mechanical, or micro-processorbased control system (or a combination thereof). The control system 322may receive (or store) inputs associated with engine operatingcharacteristics of an engine of a vehicle that includes the on-boardfuel separation system 300 and, based on the received (or stored)inputs, send control signals to, for example, one or more valves thatadjust or control the flow rates of the fuel stream 106, the heated fuelstream 306, the vapor stream 316, the liquid stream 317, or acombination thereof. The control system 322 may also be communicablycoupled to the fuel separator 314 to control, for example, operatingtemperature, pressure, or pressures, of the flash tank(s) in the fuelseparator 314. The control system 322 may also be communicably coupledto the secondary heater 308 to, for example, further add heat to theheated fuel stream 306 prior to the fuel separator 314.

Example engine operating characteristics include, for example, engineload, torque and speed and fuel specifications such as vapor-liquidratio, a vapor lock index, a drivability index, a T90 or T95 property, afuel lubricity, a fuel viscosity, or an engine speed-torque ratio, amongother examples. Such characteristics (as inputs to the control system322) may be used, at least in part, to adjust one or more operatingcharacteristics of the on-board fuel separation system 302. For example,operating pressure, temperature, or both of the heat exchanger 304, thefuel separator 324, or both, may be adjusted. Flow rates, pressures,temperature, or a combination thereof, of one or more of the illustratedfuel streams (for example, the fuel stream 106, the heated fuelstream(s), the vapor fuel stream 316, the liquid fuel stream 317, orotherwise) may also be adjusted (for example, by controlling valves, notshown, with the control system 322). By adjusting one or more componentsof the on-board fuel separation system 302 with the control system 318,the auto-ignition characteristic values of one or both of the vapor fuelstream 316 and the liquid fuel stream 317 may be adjusted, for example,to desired values according to engine operating conditions.

The illustrated vapor stream 316 and liquid stream 317 may havedifferent auto-ignition characteristic values. For example, in someaspects, the vapor stream 316 may have an auto-ignition characteristicvalue that is less than an auto-ignition characteristic value of theliquid stream 317. In some aspects, the auto-ignition characteristicvalues of the vapor stream 316 and the liquid stream 317 may be RON orcetane number.

In an example operation, the fuel stream 106 is circulated (for example,forcibly pumped, sprayed, or otherwise) to the heat exchanger 304, aswell as the vapor stream 316 output from the fuel separator 314. Heatfrom the vapor stream 316 is transferred, in the heat exchanger 304, tothe fuel stream 106 and output from the heat exchanger 304 as the heatedfuel stream 306. The vapor stream 316, which has a particularauto-ignition characteristic value (for example, a low RON relative tothe RON of the liquid stream 317), condenses in the heat exchanger 304as heat is transferred to the fuel stream 106. The condensed vaporstream 319 (now as a liquid stream with the low RON) may be circulatedto the fractional fuel tank 116 and stored for use as a fuel source foran engine (for example, engine 134).

In some aspects, prior to circulation of the fuel stream 106 to the heatexchanger 304, the fuel stream 106 may be preheated, for example, withelectric heating, heating tape, or otherwise. For example, in “coldstart” situations (for example, where the engine of the vehicle is beingstarted), the fuel stream 106 may be preheated based on an inability ofthe vapor stream 316 to provide sufficient heat, in the cold startsituation, to the fuel stream 106. In such aspects, one or more of thefuel fractions (for example, the low RON, condensed vapor phase 319 orthe high RON liquid phase 317) stored in the fractional fuel tanks 116and 114 may be used as the cold start fuel for the engine.

In some aspects, the vapor stream 316 may not completely condense to aliquid in the heat exchanger 304. In such aspects, the partiallycondensed vapor stream 319 may be further cooled to more completelycondense any remaining vapor in the stream 319. For example, the vaporin the partially condensed vapor stream 319 may be separated andcirculated to the engine with an air intake to the engine. As anotherexample, a secondary heat exchanger (not shown) such as a cooling coil,radiator, or otherwise, may further cool the vapor stream 319 (forexample, with a cold refrigerant that is part of the vehicleair-conditioning system) between the heat exchanger 304 and thefractional fuel tank 116. As yet another example, a pressure of thepartially condensed vapor stream 319 may be increased to further orfully condense the stream 319 prior to the fractional fuel tank 116.

The heated fuel stream 306 is circulated through the secondary heater308, which may or may not add additional heat to the heated fuel stream306. For example, the secondary heater 308 may be controlled (forexample, by the control system 322) to add additional heat so thatparticular auto-ignition characteristic values (for example, RON orcetane number) may be met in the vapor stream 316 and the liquid stream317.

The heated fuel stream 306 (further heated by the secondary heater 308or otherwise) is circulated through the orifice 310 and into the fuelseparator 314 as the fuel stream input 312. In some aspects, the orifice310 may be controlled (for example, by the control system 322) to adjusta pressure of the fuel input stream 312 so that particular auto-ignitioncharacteristic values (for example, RON or cetane number) may be met inthe vapor stream 316 and the liquid stream 317.

The fuel input stream 312 is circulated through the fuel separator 314and separated (for example, based on relative volatilities of thefractions of the fuel input stream 312) into the illustrated vaporstream 316 and the illustrated liquid stream 317. In some aspects, thefuel separator 314 may separate the fuel input stream 312 into multiplevapor streams and multiple liquid streams, each with a particularauto-ignition characteristic value (for example, RON or cetane number).In such aspects, the fuel separator 314 (for example, flash tanks ordistillation units or combination thereof) may have multiple separationstages.

In the illustrated implementation, the vapor phase 316 is circulated tothe power generator 318 (for example, a turbine or micro-turbine). Thevapor phase 316 drives the power generator 318 to generate power, P, andis output from the power generator 318 at a lower pressure (but still invapor phase) than that at which the phase 316 entered the generator 318.The lower pressure vapor phase 316 is circulated from the powergenerator 318 to the heat exchanger 304.

The liquid stream 317 output from the fuel separator 314, in thisexample, has an auto-ignition characteristic value (for example, RON)that is higher than the auto-ignition characteristic value of the vaporstream 316. The liquid stream 317 is circulated to the fractional fueltank 114 and stored for use as a fuel source for an engine (for example,engine 124).

FIG. 4 is a schematic illustration of another example implementation ofan on-board fuel separation system 400 according to the presentdisclosure. In some aspects, at least a portion of the system 400 may beimplemented as the on-board fuel separation system 108 in the vehicle102 shown in FIG. 1. System 400 may be similar to systems 200 and 300,shown in FIGS. 2 and 3, but also includes a power generator 424, a twostage heat exchanger system, and a two stage fuel separator system.Thus, the system 400 may further separate the vapor stream, obtainedfrom the first flash tank, to high RON oxygenates and low RON compounds.

The illustrated on-board fuel separation system 400 includes an on-boardfuel separation sub-assembly 402 (designated by the dashed line) thatincludes several components. As illustrated, the fuel stream 106 may bereceived at a first-stage heat exchanger 404 (for example, a plate andframe heat exchanger, shell and tube heat exchanger, fin and tube heatexchanger, or otherwise). The first-stage heat exchanger 404 alsoreceives an input of a vapor fuel stream 428 (for example, a low RONcompounds vapor stream) that is output from the on-board fuel separationsub-assembly 402 and circulated back to the first-stage heat exchanger404.

The first-stage heat exchanger 404 outputs a heated fuel stream 406 to asecond-stage heat exchanger 408 (for example, a plate and frame heatexchanger, shell and tube heat exchanger, fin and tube heat exchanger,or otherwise). The second-stage heat exchanger 408 receives the heatedfuel stream 406 and a combined liquid fuel stream that includes a highRON liquid stream 430 output from a first stage fuel separator 418 and ahigh RON oxygenate fuel stream 432 from a second-stage fuel separator422. In this example implementation, these two fuel streams combine andare circulated to the second-stage heat exchanger 408 to provide furtherheat to the heated fuel stream 406 prior to fuel separation. From thesecond-stage heat exchanger 408, a combined high RON fuel stream 417 iscirculated to the fractional fuel tank 114 (for example, a high RON fueltank). In alternative implementations, one or both of the high RONliquid stream 430 and the high RON oxygenate fuel stream 432 may besupplied to the fractional fuel tank 114 without passing through thesecond-stage heat exchanger 408.

In another example implementation, the order of the first- andsecond-stage heat exchangers may be reversed. For example, a first-stageheat exchanger 404 may receive the fuel stream 106 and a combined liquidfuel stream that includes a high RON liquid stream 430 output from afirst stage fuel separator 418 and a high RON oxygenate fuel stream 432from a second-stage fuel separator 422. The first-stage heat exchanger404 outputs the heated fuel stream 406 to the second-stage heatexchanger 408, which receives an input of a vapor fuel stream 428 (forexample, a low RON compounds vapor stream) that is output from theon-board fuel separation sub-assembly 402.

The further heated fuel stream 410 is fluidly coupled to a secondaryheater 412 (for example, hot coolant, hot exhaust gas, electric heateror otherwise) that can controllably provide additional heat to the fuelstream 410. An orifice 414 (for example, valve, fixed orifice, variableorifice, or otherwise) is fluidly coupled between the heater 412 and afirst-stage fuel separator 418. A fuel stream input 416 from the orifice414 provides the further heated fuel stream 410 (for example, atincreased or decreased pressure) to the first-stage fuel separator 418.

The first-stage fuel separator 414, in the illustrated implementation ofsystem 400, separates the fuel stream input 416 into two fuel fractionstreams: a low RON vapor fuel stream 420 and a high RON liquid fuelstream 430 based on, for example, a volatility of the fuel stream input416. In this example, the high RON liquid fuel stream 430 may besupplied to the fractional fuel tank 114 as described previously.

As illustrated in this implementation, the separated low RON vapor fuelstream 420 is fluidly coupled to a second-stage fuel separator 422. Inthis example, the second-stage fuel separator 422 may separate (forexample, based on volatility of the vapor stream 420) the vapor stream420 into a low RON compound stream 428 and a high RON oxygenate stream432. As described previously, the high RON oxygenate stream 432 maycombine with the high RON liquid stream (for example, through thesecond-stage heat exchanger 408 or the fractional fuel tank 114).

The illustrated fuel separators 418 and 422 may be flash distillationassemblies that separate the input fuel streams (for example, fuelstream 412 and vapor stream 420) into at least two separate fuelfractions based on a relative volatility of the fractional components ofthe input fuel stream. In some aspects, each flash distillation assemblymay include one or more flash tanks that are fitted with screens orsimilar internal structures to prevent or reduce liquid droplets (mist)from being carried with a vapor stream within the fuel separator. Insome aspects, each flash distillation assembly may be a compactdistillation unit filled with structured or random packing, or withtrays, to improve the separation and prevent or reduce mist carryoverinto a vapor stream. Further, in some aspects, a number of flash tanksin each flash distillation assembly may be determined by, for example,components of the fuel stream 106 (for example, linear alkanes, branchedalkanes, cyclic alkanes, alkenes, aromatics) and their relativevolatility, the volatility of additives of the fuel stream 106 such asoxygenates, desired auto-ignition characteristic value of a resultantlow RON stream or high RON stream, relative flow rates of the resultantlow RON stream or high RON stream, or a combination thereof.

In some aspects, one or both of the first-stage fuel separator 418 andsecond-stage fuel separator 422 may be operated at a vacuum. Forexample, in some implementations in which a particular auto-ignitioncharacteristic value is desired, the first-stage fuel separator 414, thesecond-stage fuel separator 422, or both, may be operated under a vacuum(for example, lower than ambient operating pressure) to recoverincreased high volatility components of the fuel stream input 416 or lowRON vapor stream 420.

A power generator 424, in this example implementation, is fluidlycoupled within the low RON compounds (vapor) stream 428 between thesecond-stage fuel separator 422 and the first-stage heat exchanger 404.The power generator 424, in some aspects, may be a turbine ormicro-turbine mounted in the vehicle that receives the low RON compounds(vapor) stream 428 at a particular pressure, which turns the turbine togenerate power, P, and outputs the low RON compounds (vapor) stream 428at a reduced pressure to the first-stage heat exchanger 404. Theauto-ignition characteristic value (for example, RON or cetane number)of the low RON compounds (vapor) stream 428 may remain unchanged orsubstantially unchanged as the low RON compounds (vapor) stream 428rotates the power generator 424 and loses pressure.

The illustrated system 400 also includes a control system 426 that iscommunicably coupled to the on-board fuel separation sub-assembly 402(for example, communicably coupled to control one or more of thecomponents, as well as unillustrated components, of the on-board fuelseparation sub-assembly 402). In some aspects, the control system 426may be a mechanical, pneumatic, electro-mechanical, or micro-processorbased control system (or a combination thereof). The control system 426may receive (or store) inputs associated with engine operatingcharacteristics of an engine of a vehicle that includes the on-boardfuel separation system 400 and, based on the received (or stored)inputs, send control signals to, for example, one or more valves thatadjust or control the flow rates of the fuel stream 106, the heated fuelstreams 406, 410, and/or 416, the low RON vapor stream 420, the high RONliquid stream 430, the low RON compounds stream 428, the high RONoxygenate stream 432, or a combination thereof. The control system 426may also be communicably coupled to the first-stage fuel separator 418,the second-stage fuel separator 422, or both, to control, for example,operating pressure, or pressures, of the flash tank(s) in the fuelseparators 418 and 422. The control system 426 may also be communicablycoupled to the secondary heater 412 to, for example, further add heat tothe heated fuel stream 410 prior to the first-stage fuel separator 418.

Example engine operating characteristics include, for example, engineload, torque and speed and fuel specifications such as vapor-liquidratio, a vapor lock index, a drivability index, a T90 or T95 property, afuel lubricity, a fuel viscosity, or an engine speed-torque ratio, amongother examples. Such characteristics (as inputs to the control system426) may be used, at least in part, to adjust one or more operatingcharacteristics of the on-board fuel separation system 402. For example,operating pressure, temperature, or both of the first or second stageheat exchangers 404/408, the first or second stage fuel separators418/422, or combinations thereof, may be adjusted. Flow rates,pressures, temperature, or a combination thereof, of one or more of theillustrated fuel streams (for example, the fuel stream 106, the heatedfuel stream(s), the low RON vapor fuel stream 420, the high RON liquidfuel stream 430, the low RON compounds vapor stream 428, the high RONoxygenates stream 432, or otherwise) may also be adjusted (for example,by controlling valves, not shown, with the control system 426). Byadjusting one or more components of the on-board fuel separation system402 with the control system 426, the auto-ignition characteristic valuesof one or both of the vapor fuel stream 420 and the liquid fuel stream430 may be adjusted, for example, to desired values according to engineoperating conditions.

In an example operation, the fuel stream 106 and the low RON compoundsvapor stream 428 are circulated (for example, forcibly pumped, sprayed,or otherwise) to the first-stage heat exchanger 404. Heat from the vaporstream 428 is transferred, in the first-stage heat exchanger 404, to thefuel stream 106 and output from the first-stage heat exchanger 404 asthe heated fuel stream 406. The vapor stream 428, which has a particularauto-ignition characteristic value (for example, a low RON relative tothe RON of the liquid stream 430), condenses in the first-stage heatexchanger 404 as heat is transferred to the fuel stream 106. Thecondensed vapor stream 419 (now as a liquid stream with the low RON) maybe circulated to the fractional fuel tank 116 and stored for use as afuel source for an engine (for example, engine 124).

In some aspects, prior to circulation of the fuel stream 106 to thefirst-stage heat exchanger 404, the fuel stream 106 may be preheated,for example, with electric heating, heating tape, or otherwise. Forexample, in “cold start” situations (for example, where the engine ofthe vehicle is being started), the fuel stream 106 may be preheatedbased on an inability of the vapor stream 418 to provide sufficientheat, in the cold start situation, to the fuel stream 106. In suchaspects, one or more of the fuel fractions (for example, the low RON,condensed vapor phase 419 or the combined high RON liquid phase 417)stored in the fractional fuel tanks 116 and 114 may be used as the coldstart fuel for the engine.

In some aspects, the low RON compounds vapor stream 428 may notcompletely condense to a liquid in the first-stage heat exchanger 404.In such aspects, the partially condensed vapor stream 419 may be furthercooled to more completely condense any remaining vapor in the stream419. For example, the vapor in the partially condensed vapor stream 419may be separated and circulated to the engine with an air intake to theengine. As another example, a secondary heat exchanger (not shown) suchas a cooling coil, radiator, or otherwise, may further cool the vaporstream 419 (for example, with a cold refrigerant that is part of thevehicle air-conditioning system) between the first-stage heat exchanger404 and the fractional fuel tank 116. As yet another example, a pressureof the partially condensed vapor stream 419 may be increased to furtheror fully condense the stream 419 prior to the fractional fuel tank 116.

The heated fuel stream 406 is circulated through the second-stage heatexchanger 408, which also receives the combined high RON liquid stream430 and high RON oxygenate stream 432 (in this example). Heat istransferred, in the second-stage heat exchanger 408, from the combinedhigh RON streams to the heated fuel stream 406.

The further heated fuel stream 410 is circulated from the second-stageheat exchanger 408 to the secondary heater 412, which may or may not addadditional heat to the heated fuel stream 410. For example, thesecondary heater 412 may be controlled (for example, by the controlsystem 426) to add additional heat so that particular auto-ignitioncharacteristic values (for example, RON or cetane number) may be met inthe vapor stream 420 and the liquid stream 430.

The further heated fuel stream 410 (further heated by the secondaryheater 412 or otherwise) is circulated through the orifice 414 and intothe first-stage fuel separator 418 as the fuel stream input 416. In someaspects, the orifice 414 may be controlled (for example, by the controlsystem 426) to adjust a pressure of the fuel input stream 412 so thatparticular auto-ignition characteristic values (for example, RON orcetane number) may be met in the vapor stream 416 and the liquid stream417.

The fuel input stream 416 is circulated through the first-stage fuelseparator 418 and separated (for example, based on relative volatilitiesof the fractions of the fuel input stream 416) into the illustrated lowRON vapor stream 420 and the illustrated high RON liquid stream 430. Theliquid stream 430 output from the first-stage fuel separator 418, inthis example, has an auto-ignition characteristic value (for example,RON) that is higher than the auto-ignition characteristic value of thevapor stream 420. The liquid stream 430 is circulated through thesecond-stage heat exchanger 408 (along with high RON oxygenate stream432) to the fractional fuel tank 114 and stored for use as a fuel sourcefor an engine (for example, engine 124).

The illustrated low RON vapor stream 420 is circulated from thefirst-stage fuel separator 418 to the second-stage fuel separator 422.In the second-stage fuel separator 422, the low RON vapor stream 420 isseparated (for example, based on relative volatilities of the fractionsof the vapor stream 420) into the low RON compounds vapor stream 428 andthe high RON oxygenate stream 432. The low RON compounds vapor stream428 is then circulated to the power generator 424 to drive the generatorand produce power. Subsequently, the low RON compounds vapor stream 428is circulated (at a lower pressure) to the first-stage heat exchanger404, where it is condensed to the condensed low RON fuel stream 419 forstorage in the fractional fuel tank 416 as a fuel source for an engine(for example, engine 124).

FIGS. 5A-5C are graphs 500, 505, and 510, respectively, that illustrateresults of a simulation model of an on-board fuel separation systemaccording to the present disclosure. The simulation model which resultsare shown in graphs 500, 505, and 510 simulates an operation of anon-board fuel separation system for a vehicle that includes a heatexchanger and single stage fuel separator, for example, as shown insystem 200 in FIG. 2. In the simulation model of FIGS. 5A-5C, a fuelstream (for example, fuel stream 106) is 91 gasoline mixed with methyltertiary butyl ether (MTBE).

Graph 500 illustrates RON of a liquid fuel stream (for example, liquidstream 217) and RON of a vapor fuel stream (for example, vapor fuelstream 216) relative to an operating temperature of a fuel separator(for example, fuel separator 214). In this example, the fuel separatorof the simulation model is a single flash tank distillation unit. Asillustrated, a relative difference in RON between the liquid fuel streamand the vapor fuel stream generally increases as flash distillationincreases (up to 26 in RON difference).

Graph 505 illustrates RON of the liquid fuel stream and RON of the vaporfuel stream relative to an operating volumetric flow rate of thecondensed vapor fuel stream (for example, fuel stream 219) of the fuelseparator. As illustrated, a relative difference in RON between theliquid fuel stream and the vapor fuel stream generally increases asvolumetric flow rate of the condensed vapor fuel stream from the flashdistillation unit increases (up to 26 in RON difference).

Graph 510 illustrates heat flow rate relative to operating temperatureof the fuel separator. In graph 510, the “Required Heat” line representsthe required thermal energy per liter of incoming fuel in line 106 toachieve the RON differential at the specified temperature (for example,heat supplied to the fuel stream through heat exchanger(s), heaters, orboth). The “Coolant” line represents the available thermal energy perliter of incoming fuel in the hot coolant that could be used in heatexchanger 208. In some aspects, beyond about 80° C., this heat is notusable (in heat exchanger 208) as the temperature difference may be zeroor negative. The “Exhaust” line represents the available thermal energyper liter of incoming fuel in the exhaust gas that could be used in heatexchanger 208.

FIGS. 6A-6C are graphs 600, 605, and 610, respectively, that illustrateresults of another simulation model of an on-board fuel separationsystem according to the present disclosure. The simulation model whichresults are shown in graphs 600, 605, and 610 simulates an operation ofan on-board fuel separation system for a vehicle that includes a heatexchanger and single stage fuel separator, for example, as shown insystem 200 in FIG. 2. In the simulation model of FIGS. 6A-6C, a fuelstream (for example, fuel stream 106) is 91 gasoline without oxygenates.

Graph 600 illustrates RON of a liquid fuel stream (for example, liquidstream 217) and RON of a vapor fuel stream (for example, vapor fuelstream 216) relative to an operating temperature of a fuel separator(for example, fuel separator 214). In this example, the fuel separatorof the simulation model is a single tank flash distillation unit. Asillustrated, a relative difference in RON between the liquid fuel streamand the vapor fuel stream generally increases as flash distillationincreases (up to 29 in RON difference).

Graph 605 illustrates RON of the liquid fuel stream and RON of the vaporfuel stream relative to an operating volumetric flow rate of the vaporfuel stream (for example, fuel stream 219) of the fuel separator. Asillustrated, a relative difference in RON between the liquid fuel streamand the vapor fuel stream generally increases as volumetric flow rate ofthe condensed vapor fuel stream from the flash distillation unitincreases (up to 29 in RON difference).

Graph 610 illustrates heat flow rate relative to operating temperatureof the fuel separator. In graph 610, the “Required Heat” line representsthe required thermal energy per liter of incoming fuel in line 106 toachieve the RON differential at the specified temperature (for example,heat supplied to the fuel stream through heat exchanger(s), heaters, orboth). The “Coolant” line represents the available thermal energy perliter of incoming fuel in the hot coolant that could be used in heatexchanger 208. In some aspects, beyond about 80° C., this heat is notusable (in heat exchanger 208) as the temperature difference may be zeroor negative. The “Exhaust” line represents the available thermal energyper liter of incoming fuel in the exhaust gas that could be used in heatexchanger 208.

FIGS. 7A and 7B are graphs 700 and 705, respectively, that illustrateresults of another simulation model of an on-board fuel separationsystem according to the present disclosure. Graph 700 shows an effect ofa number of equilibrium stages in a fuel separator (for example, acompact distillation unit or a fuel separator with multiple flash tanks)on an auto-ignition characteristic value; here, RON. Graph 705 shows aneffect of a reflux ratio on an auto-ignition characteristic value; here,RON. In some aspects, in a compact distillation unit, the number ofequilibrium stages and the reflux ratio are additional design variables,which can be varied to vary RON of the output streams (for example,vapor and liquid streams).

FIG. 8 is a schematic illustration of an example controller 800 (orcontrol system) for an on-board fuel separation system. For example, thecontroller 800 can be used for the operations described previously, forexample as or as part of the control systems 218, 322, 426 or othercontrollers described herein. For example, the controller 800 may becommunicably coupled with, or as a part of, one or both of a vehicleengine and on-board fuel separation system as described herein.

The controller 800 is intended to include various forms of digitalcomputers, such as printed circuit boards (PCB), processors, digitalcircuitry, or otherwise that is part of a vehicle. Additionally thesystem can include portable storage media, such as, Universal Serial Bus(USB) flash drives. For example, the USB flash drives may storeoperating systems and other applications. The USB flash drives caninclude input/output components, such as a wireless transmitter or USBconnector that may be inserted into a USB port of another computingdevice.

The controller 800 includes a processor 810, a memory 820, a storagedevice 830, and an input/output device 840. Each of the components 810,820, 830, and 840 are interconnected using a system bus 850. Theprocessor 810 is capable of processing instructions for execution withinthe controller 800. The processor may be designed using any of a numberof architectures. For example, the processor 810 may be a CISC (ComplexInstruction Set Computers) processor, a RISC (Reduced Instruction SetComputer) processor, or a MISC (Minimal Instruction Set Computer)processor.

In one implementation, the processor 810 is a single-threaded processor.In another implementation, the processor 810 is a multi-threadedprocessor. The processor 810 is capable of processing instructionsstored in the memory 820 or on the storage device 830 to displaygraphical information for a user interface on the input/output device840.

The memory 820 stores information within the controller 800. In oneimplementation, the memory 820 is a computer-readable medium. In oneimplementation, the memory 820 is a volatile memory unit. In anotherimplementation, the memory 820 is a non-volatile memory unit.

The storage device 830 is capable of providing mass storage for thecontroller 800. In one implementation, the storage device 830 is acomputer-readable medium. In various different implementations, thestorage device 830 may be a floppy disk device, a hard disk device, anoptical disk device, or a tape device.

The input/output device 840 provides input/output operations for thecontroller 800. In one implementation, the input/output device 840includes a keyboard and/or pointing device. In another implementation,the input/output device 840 includes a display unit for displayinggraphical user interfaces.

The features described can be implemented in digital electroniccircuitry, or in computer hardware, firmware, software, or incombinations of them. The apparatus can be implemented in a computerprogram product tangibly embodied in an information carrier, forexample, in a machine-readable storage device for execution by aprogrammable processor; and method steps can be performed by aprogrammable processor executing a program of instructions to performfunctions of the described implementations by operating on input dataand generating output. The described features can be implementedadvantageously in one or more computer programs that are executable on aprogrammable system including at least one programmable processorcoupled to receive data and instructions from, and to transmit data andinstructions to, a data storage system, at least one input device, andat least one output device. A computer program is a set of instructionsthat can be used, directly or indirectly, in a computer to perform acertain activity or bring about a certain result. A computer program canbe written in any form of programming language, including compiled orinterpreted languages, and it can be deployed in any form, including asa stand-alone program or as a module, component, subroutine, or otherunit suitable for use in a computing environment.

Suitable processors for the execution of a program of instructionsinclude, by way of example, both general and special purposemicroprocessors, and the sole processor or one of multiple processors ofany kind of computer. Generally, a processor will receive instructionsand data from a read-only memory or a random access memory or both. Theessential elements of a computer are a processor for executinginstructions and one or more memories for storing instructions and data.Generally, a computer will also include, or be operatively coupled tocommunicate with, one or more mass storage devices for storing datafiles; such devices include magnetic disks, such as internal hard disksand removable disks; magneto-optical disks; and optical disks. Storagedevices suitable for tangibly embodying computer program instructionsand data include all forms of non-volatile memory, including by way ofexample semiconductor memory devices, such as EPROM, EEPROM, and flashmemory devices; magnetic disks such as internal hard disks and removabledisks; magneto-optical disks; and CD-ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,ASICs (application-specific integrated circuits).

To provide for interaction with a user, the features can be implementedon a computer having a display device such as a CRT (cathode ray tube)or LCD (liquid crystal display) monitor for displaying information tothe user and a keyboard and a pointing device such as a mouse or atrackball by which the user can provide input to the computer.Additionally, such activities can be implemented via touchscreenflat-panel displays and other appropriate mechanisms.

The features can be implemented in a control system that includes aback-end component, such as a data server, or that includes a middlewarecomponent, such as an application server or an Internet server, or thatincludes a front-end component, such as a client computer having agraphical user interface or an Internet browser, or any combination ofthem. The components of the system can be connected by any form ormedium of digital data communication such as a communication network.Examples of communication networks include a local area network (“LAN”),a wide area network (“WAN”), peer-to-peer networks (having ad-hoc orstatic members), grid computing infrastructures, and the Internet.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular implementations of particularinventions. Certain features that are described in this specification inthe context of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresthat are described in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the implementations described above should not beunderstood as requiring such separation in all implementations, and itshould be understood that the described program components and systemscan generally be integrated together in a single software product orpackaged into multiple software products.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. For example, exampleoperations, methods, or processes described herein may include moresteps or fewer steps than those described. Further, the steps in suchexample operations, methods, or processes may be performed in differentsuccessions than that described or illustrated in the figures.Accordingly, other implementations are within the scope of the followingclaims.

What is claimed is:
 1. A fuel separation system, comprising: a fuelseparator configured to receive a fuel stream and separate the fuelstream, based on a volatility of the fuel stream, into a vapor streamdefined by a first auto-ignition characteristic value and a first liquidstream defined by a second auto-ignition characteristic value, thesecond auto-ignition characteristic value greater than the firstauto-ignition characteristic value; and a heat exchanger fluidly coupledbetween a fuel input of the fuel stream and the fuel separator, the heatexchanger configured to transfer heat from the vapor stream to the fuelstream, and output a heated fuel stream to the fuel separator and asecond liquid stream defined by the first auto-ignition characteristicvalue.
 2. The fuel separation system of claim 1, wherein the heatexchanger is configured to condense the vapor stream to the secondliquid stream defined by the first auto-ignition characteristic value.3. The fuel separation system of claim 1, further comprising a heatercoupled between the heat exchanger and the fuel separator and configuredto receive the heated fuel stream and further heat the heated fuelstream.
 4. The fuel separation system of claim 1, further comprising avariable orifice fluidly coupled between the heat exchanger and the fuelseparator.
 5. The fuel separation system of claim 4, further comprisinga controller operatively coupled to control at least one of the fuelseparator or the variable orifice to vary a volumetric flow rate of atleast one of the heated fuel stream, the vapor stream, or the firstliquid stream.
 6. The fuel separation system of claim 5, wherein thecontroller is configured to vary at least one of the first auto-ignitioncharacteristic value or the second auto-ignition characteristic valuebased, at least in part, on at least one engine operating condition. 7.The fuel separation system of claim 6, wherein the at least one engineoperating condition comprises an engine load, an engine torque, andengine speed, a fuel vapor-liquid ratio, a fuel vapor lock index, a fueldrivability index, a fuel T90 or T95 property, a fuel lubricity, a fuelviscosity, or an engine speed-torque ratio.
 8. The fuel separationsystem of claim 1, wherein the fuel separator comprises a flashdistillation separator.
 9. The fuel separation system of claim 1,wherein the fuel separator comprises a first stage fuel separator and asecond stage fuel separator.
 10. The fuel separation system of claim 9,wherein the first stage fuel separator is configured to receive the fuelstream and separate the fuel stream, based on the volatility of the fuelstream, into the vapor stream defined by the first auto-ignitioncharacteristic value and the first liquid stream defined by the secondauto-ignition characteristic value, and the second stage fuel separatoris configured to separate the vapor stream into an oxygenate stream anda compound stream.
 11. The fuel separation system of claim 10, whereinthe second stage fuel separator is configured to direct the oxygenatestream to combine with the first liquid stream, and to direct thecompound stream to the heat exchanger.
 12. The fuel separation system ofclaim 1, wherein the first auto-ignition characteristic value comprisesa first research octane number (RON) or a first cetane number, and thesecond auto-ignition characteristic value comprises a second RON or asecond cetane number.
 13. A method for separating a fuel on-board avehicle, comprising: separating, with a fuel separator, a heated fuelstream into a vapor stream and a first liquid stream based on avolatility of the fuel stream, the vapor stream defined by a firstauto-ignition characteristic value and the first liquid stream definedby a second auto-ignition characteristic value, the second auto-ignitioncharacteristic value greater than the first auto-ignition characteristicvalue; supplying an unheated fuel stream and the vapor stream from thefuel separator to a heat exchanger; transferring heat from the vaporstream to the unheated fuel stream to heat the unheated fuel stream;supplying the heated fuel stream to the fuel separator; and supplying asecond liquid stream defined by the first auto-ignition characteristicvalue from the heat exchanger.
 14. The method of claim 13, furthercomprising condensing, with the heat exchanger, the vapor stream to formthe second liquid stream.
 15. The method of claim 13, furthercomprising: further heating the heated fuel stream; and supplying thefurther heated fuel stream to the fuel separator.
 16. The method ofclaim 15, wherein further heating the heated fuel stream comprises atleast one of: heating the heated fuel stream with an electric heater;heating the heated fuel stream in a heat exchanger with the first liquidstream; or heating the heated fuel stream in a heat exchanger with anengine exhaust gas stream.
 17. The method of claim 13, furthercomprising circulating the heated fuel stream through a variable orificefluidly coupled between the heat exchanger and the fuel separator. 18.The method of claim 17, further comprising controlling at least one ofthe fuel separator or the variable orifice to vary a volumetric flowrate of at least one of the heated fuel stream, the vapor stream, or thefirst liquid stream.
 19. The method of claim 18, further comprisingvarying at least one of the first auto-ignition characteristic value orthe second auto-ignition characteristic value based, at least in part,on at least one engine operating condition.
 20. The method of claim 18,wherein the at least one engine operating condition comprises an engineload, an engine torque, an engine speed, a fuel vapor-liquid ratio, afuel vapor lock index, a fuel drivability index, a fuel T90 or T95property, a fuel lubricity, a fuel viscosity, or an engine speed-torqueratio.
 21. The method of claim 13, wherein the fuel separator comprisesa flash distillation separator.
 22. The method of claim 13, wherein thefuel separator comprises a first stage fuel separator and a second stagefuel separator.
 23. The method of claim 22, further comprising:separating, with the first stage fuel separator, the heated fuel streaminto the vapor stream defined by the first auto-ignition characteristicvalue and the first liquid stream defined by the second auto-ignitioncharacteristic value, based on the volatility of the fuel stream, andseparating, with the second stage fuel separator, the vapor stream intoan oxygenate stream and a compound stream.
 24. The method of claim 23,further comprising: combining the oxygenate stream with the first liquidstream; and supplying the compound stream to the heat exchanger.
 25. Themethod of claim 13, wherein the first auto-ignition characteristic valuecomprises a first research octane number (RON) or a first cetane number,and the second auto-ignition characteristic value comprises a second RONor a second cetane number.
 26. A vehicle system, comprising a vehicle; afuel-powered internal combustion engine mounted in the vehicle; anon-board fuel separation system, comprising: a fuel separator configuredto receive a fuel stored in the vehicle and separate the fuel, based ona volatility of the fuel stream, into a vapor stream defined by a firstauto-ignition characteristic value and a first liquid stream defined bya second auto-ignition characteristic value, the second auto-ignitioncharacteristic value greater than the first auto-ignition characteristicvalue; and a heat exchanger fluidly coupled between a fuel input of thefuel and the fuel separator, the heat exchanger configured to transferheat from the vapor stream to the fuel, and output a heated fuel streamto the fuel separator and a second liquid stream defined by the firstauto-ignition characteristic value; a first fuel tank fluidly coupledbetween the engine and the fuel separator to store the first liquidstream output from the fuel separator; and a second fuel tank fluidlycoupled between the engine and the heat exchanger to store the secondliquid stream output from the heat exchanger.
 27. The vehicle system ofclaim 26, wherein the heat exchanger is configured to condense the vaporstream to the second liquid stream defined by the first auto-ignitioncharacteristic value.
 28. The vehicle system of claim 27, furthercomprising a controller operatively coupled to control at least one ofthe fuel separator or the variable orifice to vary a volumetric flowrate of at least one of the heated fuel stream, the vapor stream, or thefirst liquid stream.
 29. The vehicle system of claim 28, wherein thecontroller is configured to vary at least one of the first auto-ignitioncharacteristic value or the second auto-ignition characteristic valuebased, at least in part, on at least one engine operating condition ofthe engine.
 30. The vehicle system of claim 29, wherein the at least oneengine operating condition comprises an engine load, an engine torque,an engine speed, a fuel vapor-liquid ratio, a fuel vapor lock index, afuel drivability index, a fuel T90 or T95 property, a fuel lubricity, afuel viscosity, or an engine speed-torque ratio.
 31. The vehicle systemof claim 26, further comprising a turbine that comprises an inputfluidly coupled to the fuel separator and output fluidly coupled to theheat exchanger and configured to receive the vapor stream from the fuelseparator and generate electrical power based on a pressure differenceof the vapor stream between the input and the output.
 32. The vehiclesystem of claim 26, wherein the first auto-ignition characteristic valuecomprises a first research octane number (RON) or a first cetane number,and the second auto-ignition characteristic value comprises a second RONor a second cetane number.